This combination of photos provided by the Federal Bureau of Investigation shows William James Vahey in 1995, left, and 1986. The FBI is asking for help to identify at least 90 victims of Vahey's, a suspected serial child predator who worked in American schools worldwide for four decades. Vahey, 64, killed himself in Luverne, Minn., on March 21.

., Associated Press

An outside view of the Southbank International School in central London where suspected child molester William James Vahey taught for a four-year term, Thursday, April 24, 2014. British police is helping with a FBI global investigation to identify and trace victims of a suspected pedophile teacher, William James Vahey, who killed himself in March in Luverne Minnesota. (AP Photo/Sang Tan)

Sang Tan, ASSOCIATED PRESS - AP

London school says students abused by teacher who killed himself in Minn.

Associated Press

April 24, 2014 - 2:05 PM

LONDON — A British private school said Thursday that images of between 50 and 60 of its students were found on the computer drive of an American suspected child predator who killed himself last month.

The FBI has asked for international help to find victims of William Vahey, who worked at 10 international schools around the world over four decades.

Graham Lacey, executive principal of the Southbank International School in London, where Vahey taught history and geography between 2009 and 2013, said staff learned of the images Thursday.

"As a staff, we feel upset, angry and betrayed," Lacey wrote in a letter to parents. "We can only imagine what you as parents must feel."

Vahey, 64, committed suicide March 21 in Luverne, Minnesota, two days after U.S. agents filed for a warrant to search his computer thumb drive.

The FBI said the device contained pornographic images of at least 90 boys, aged 12 to 14, who appeared to be drugged and unconscious.

In a statement, the FBI said Vahey had confessed to an administrator at his most recent school "that he was molested as a child and had preyed on boys his entire life, giving them sleeping pills prior to the molestation."

The FBI said the photos dated from 2008 or after, but that Vahey may have abused children for decades.

The agency said Vahey was jailed for child molestation in California in 1969. Lacey said Vahey had undergone a criminal records check before he began working in London, but that it hadn't found anything of concern.

British police said they had searched a London property in connection with the case and were working to identify and support potential victims.

Vahey had residences in London and Hilton Head Island, South Carolina.